Automotive manual transmissions employ synchronizer torque-transmitting mechanisms to establish the torque paths from a transmission input shaft to a transmission output shaft. Manual transmissions are generally countershaft-type transmissions wherein one of the first ratio gears is disposed on a main or central shaft and the other first ratio gear that meshes with the first ratio gear is supported on a countershaft parallel with the main shaft. The ratio gears mesh such that a plurality of gear ratios can be established between the input shaft and the output shaft with the power flow passing through the main shaft and countershaft.
A plurality of synchronizer clutches is employed on one of the shafts to permit connection and disconnection of one of the sets of ratio gears therewith. When the ratio gear is connected with the shaft, the mating gears between the central shaft and the countershaft transmit torque and speed between the shafts and to the output shaft. Each set of ratio gears has a synchronizer clutch which is a device for controlling the on-coming gear ratio to permit synchronization between the gear member and the shaft on which it is rotatably mounted. Synchronizers are well-known devices and generally employ a blocker ring, which does not allow the two portions of the synchronizers to engage until a common speed is arrived at between the two members. One of the synchronizing members is connected to an input to the gear and the other members are connected to the gear itself.
The external or outer sleeve of the synchronizer slides into the blocker ring, which engages a friction device to bring the on-coming gear up to speed and prevents completion of the shift until the speed synchronization is formed. The friction device is generally a cone clutch, which abuts a cone surface on the on-coming member. The sleeve enforces engagement of the cone clutch with the cone surface to establish speed synchronization therebetween. When the conical elements are synchronized, the sleeve passes through the blocker ring and engages a splined member that is drivingly connected with one of the ratio gears.